Looks quite nice. I suppose you have the skills to develop something that might be as nice as SuperCycle 64 (the best racing game on the C64 so far).
I had a look at Speed King and indeed the way the track was done resembles that of Super Cycle. I doesn't need to be a motorcycle racing game, but I like the way the track graphics in Super Cycle or Pitstop II was done. It goes deeper into the background. This paired with effects like fog, rain, snow, road barriers, tunnels and objects on the side, maybe the need to refuel would be nice as well. So to say the ultimate racing game that tops titles like those from the 80s. The Great American Cross Country Road Race is another inspiration. To have more space for the racing graphics, you could put parts of the displays, like KMH or KM and CARS into the border. Hires graphics would also be awesome. The amount of games that are still colorful using hires graphics is rising as well. And if you need more space use EasyFlash-cartridge. Well lots of challenges for you ;)
Well, I see that you continue to improve this game. Saw another video yesterday of Buggy Boy, another example of how good track graphics could be. It's in the same class as Speed King, Pitstop II and Super Cycle, if you ask me. Maybe Hires GFX is another way to improve things further. So far, I don't remember any Hires GFX racer on the C64. Good luck and best regards.